Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.74	11.158%	$125.3195	$125.32	$125.30	$125.30
Purchase #2	$141.30	4.656%	$147.8789	$147.88	$147.90	$147.90
Purchase #3	$196.92	11.531%	$219.6268	$219.63	$219.65	$219.60
Purchase #4	$67.72	12.712%	$76.3286	$76.33	$76.35	$76.30
Purchase #5	$174.92	13.386%	$198.3348	$198.33	$198.35	$198.30
Purchase #6	$105.77	9.820%	$116.1566	$116.16	$116.15	$116.20
Purchase #7	$156.27	7.636%	$168.2028	$168.20	$168.20	$168.20
7 purchase totals =	$955.64		$1,051.8480	$1,051.85	$1,051.90	$1,051.80